Transformer construction



Jan. 29,1935. E. KERN TRANSFORMER CONSTRUGTI ON Filed NOV. 11, 1929Patented Jan. 29, 1935 UNITED STATES PATENT OFFICE TRANSFORMERCONSTRUCTION Erwin Kern,

Wettingen, Switzerland, assignor to Aktiengesellschaft Brown Boveri &Cie., Baden, Switzerland, a joint-stock company of SwitzerlandApplication November 11, 1929, Serial No. 406,244 In Germany November24, 1928 5 Claims.

- tems as will maintain a constant voltage in the direct current outputcircuit of the system, regardless of the load upon the direct currentcircuit.

It has been found that the usual electric power rectifying system :ofthe metallic vapor type is subject to a steep voltage rise when the loadon the direct current circuit drops from the usual load to practicallyno load. Such voltage increase has such an objectionable effect on theapparatus connected with the system, that various methods have beenproposed to avoid the steep voltage rise. Among such methods were theprovision of absorption reactance coils which were arranged to besupplied with a current of the third harmonic taken from a highlysaturated transformer, the primary of which transformer was usuallyconnected in star and the secondary of which was usually connected inopen delta. Another method for preventing a steep voltage rise, at lowload, in electric power rectifiers was the'connection of single phasetransformers in combination with absorption reactance coils. Acomparatively larger amount of space was, however, required to properlyarrange the rectifier supply transformer, the single phase excitationtransformers and the absorption reactance coils.

It has been found by applicant that the third harmonic in the supplytransformer for the rectifier may itself be utilized to prevent a steepvoltage rise at low'load by connecting auxiliary windings, divided intotwo portions to the star points of the secondary windings of a highlysaturated multi-phase transformer. The auxiliary windings are soproportioned that the third harmonic current induced therein opposes thethird harmonic current induced in the secondary winding and is, atleast, of the same value so that the phase of the third harmonic in thesecondary is rotated about 180.

It is, therefore, among the objects of the present invention to providean electric power rectifying system in which the voltage will bemaintained substantially constant, regardless of the load upon therectifier.

Another object of the invention is to provide a transformer supplysystem for the anodes of an electric power rectifier which system, as aunit, will contain all of the windings necessary, both for properlytransforming the current supply to the rectifier and for preventing avoltage rise at loads below a predetermined value in the rectifier.

A further object of the invention is to provide a transformer unit foran electric power rectifying system which will be provided with primary,secondary and auxiliary windings, arranged in such a manner that thethird harmonic current therein will be utilized to prevent a voltagerise at loads below a predetermined value without the addition ofabsorption re- 10 actance coils, single phase transformers or otherdevices.

Objects and advantages, other than those above set forth, will beapparent in the following description and in the drawing, whichdiagrammatically shows an embodiment of the present invention.

Referring more particularly to the drawing by characters of reference,the reference numeral 1 indicates a multi-phase alternating current sup-2 ply system connected by means of a current transformer structureindicated generally at 2 to a rectifier of the metallic vapor type,schema-tically shown at 3, which supplies a direct current consumingdevice 4, connected by means of con- 2 ductors 5 and 6 to thetransformer unit 2, and to the cathode of the rectifier 3 to form adirect current circuit.

The alternating current supply system includes phases 10, 11 and 12which are connected with 3 the several windings l4, l5 and 16, forming astar-connected primary winding 17 of the current transforming unit 2.The secondary winding 18 is divided into a plurality of portions 20, 21,22, 23, 24 and 25 which are so connected as 3 to form two star-connectedportions supplying the anodes of the rectifier 3.

Auxiliary windings 19, 19 having the several coils 30, 31, 32, 33, 34,35, are arranged in adjacent relation with the primary winding 17 and 4the secondary winding 18 in such manner that the neutral point of thesecondary coils 20, 21 and 22 is series-connected with one end of thecoils 33, 34 and 35 and the neutral point of the coils 23, 24 and 25 ofthe second portion of the 4 secondary winding 18 is connected with oneend of the series connected coils 32, 31, 30. The third harmonic currentinduced in the secondary winding 18 is in opposition to that induced inthe auxiliary windings 19 and 19' so that all possibilities 5 of avoltage rise at loads below a predetermined value in the rectifiercurrent circuit are decreased to a negligible value. If the auxiliarywindings 19 and 19' are so proportioned that the third harmonic voltageoccurring therein is greater in 5 lopnosecac thc f r thelpu pqs o rate91 Oilsaid anod ings and respectively conduc its action than that of thesecondary winding 18 then the phase of the third harmonic in thesecondary of the transformer is rotated about 180 and is, therefore,brought into the proper position. The transformer structure 2 may be ofthe type arrangement core, or may be of the shell, type arrangementasmay be most desirable. the nection h wnlt he au ilia W n ings 19 and19, the special advantage is obtained that the direct currentmagnetization of the,

transformer core is compensated by thecurrent flow through the severalcoils oi the auiii liary windings 19 and 19.

Although but one embodiment of this invention has been illustrated andLdescribed, ,itwillgibe.

inannerlas to inhibit a vvoltage rise at loads below a predeterminedvalue on said rectifier.

2. In an electric power rectiiying system, "a u t -pha e a r at n currens st m, nelec- .tric current rectifiersupplying a direct currentcircuit, and a unitary trans formerstructure,QOn" necting said supplysystem and said rectirlelj $011 p i n a, pr m ry windin sec nda wind ngand auxiliary windings inductively coupledljwith. .said primary andsai dsecondary windings to, produce a, third. harmonic voltage saidjauniliarywindings, said aimiliary windings be ng soQar- 1 ranged relative to saidsecondary windings' as to 1 cause the third harmonicsin thawindings toon, said rectifier.

3. In combination with a source of polyphase alt rnatin .cur ntad re teur gn gq i c l l cit ic rr re t f n .aiis ia i cam si es a plurality ofanodes, and a transformer, compris-,.

ing ,a, star connectedpglrnalli withsaidwsource,of currenta ingsrespectivelyhconnec t d :e a ch indiing c poll/phase r. conn cte roup rear utali y of auxiliary windings arranged as two gr. Seri s connected,polyp hase windings c up e .w mai rim nd se ondary w th ne trali intonne t fa pl of l in ng, ie

bi in f voltage riseat loads b low a predeterm ed al ue s and arrange toforjni two of said groups of secondary windings and to said work circuitand each arranged in such manner that harmonic voltages induced thereinoppose harmonic voltages induced in the group of secondary windingsconductively connected therewith to thereby inhibit voltage rise in saidwork circuitduring loads thereon below. a predeter- 4. In combinationwith a source of alternatcurrent, a direct current work circuit, elec-'jtr ic icurrent rectifying apparatus comprising a plurality of anodes,and a highly saturated trans- ,for ner comprising ,a primary windingconnected ith w v sour jce 'q'f fcurrent, and a secondary windingarrangedfvltolform two star connected groups of polyphasecoil sectionsrespectively connected eacli to aseparate one of said anodes, of Iliarywindings arranged as two ected groups inductively coupled opendelta conn with saidse'condary winding, the respective said 9 49 F e lieiyw n .i connect eachtofthe to point connefction of a'di'fiei e'nt oneof said groupsfof fcoil sections are ca work a ea. 111 m. fi e aatiharmonic voltages induced'ther X'ce ed in mag-1 a bei nd c ye nitude andqpppscinpbaset 1r harmonic voltages induced in the'group' ofsaidcoilsections con- I V ductivelyconnected therewith whereby the thirdesi lt e s re j aidhar c d substantially 180 re a we ar iba ffv svoltages vis"(; 1ispl 'ihsfth r n, coil sectioiisf "5. Inan electriccurrentrectifying system, a source of polyphase' alt fi tin urrentadirect ctric current marten: can; 1

apparatus compr singa plurality of anodes, and

a he, i-sati fie twin-i i el t rners w it e m ris i a s r e na efia i imd ssem- 'th' s dsource of current, a secondary e iip 'c l the said codistributed with respect to the grou 'bfco 1* V i tions conductiyelyconnected therewith in such f therein exceedfin:magnitude'andop oseiii'pliase thirdhai'm'o'nic"voltages induced in thesai'd coil ethirdihar 'ni'c voltage resultii'ig'ifroiii'said siaidcoil'sctioiisf t tifl e xe T e ta enera, PQWPMSB, an e i e lar 1 e to the third; voltagesinduced maytomeaeatnrewau here-

